National and Subnational estimates for the United States of America

Identifying changes in the reproduction number, rate of spread, and doubling time during the course of the COVID-19 outbreak whilst accounting for potential biases due to delays in case reporting both nationally and subnationally in the United States of America. These results are impacted by changes in testing effort, increases and decreases in testing effort will increase and decrease reproduction number estimates respectively (see Methods for further explanation).

Table of Contents


Expected daily cases by region


Figure 1: The results of the latest reproduction number estimates (based on estimated cases with a date of infection on the 2020-03-21) in the United States of America, stratified by state, can be summarised by whether cases are likely increasing or decreasing. This represents the strength of the evidence that the reproduction number in each region is greater than or less than 1, respectively.

National summary

Summary (estimates as of the 2020-03-21)

Estimate
New infections 22748 (13251 – 32240)
Expected change in daily cases Increasing
Effective reproduction no. 1.4 (1 – 1.8)
Doubling time (days) 9.2 (4.8 – 100)
Adjusted R-squared 0.73 (0.22 – 1)


Table 1: Latest estimates (as of the 2020-03-21) of the number of cases by date of infection, the expected change in daily cases, the effective reproduction number, the doubling time, and the adjusted R-squared of the exponential fit. The mean and 90% credible interval is shown for each numeric estimate.

Reported and estimated cases by date of onset and time-varying reproduction number estimates


Figure 2: A.) Cases by date of report (bars) and estimated cases by date of infection. B.) Time-varying estimate of the effective reproduction number. Light grey ribbon = 90% credible interval. Estimates are shown until the 2020-03-21.Dark grey ribbon = 50% credible interval. Confidence in the estimated values is indicated by shading with reduced shading corresponding to reduced confidence.

Time-varying rate of spread and doubling time


Figure 3: A.) Time-varying estimate of the rate of spread, B.) Time-varying estimate of the doubling time in days (note that when the rate of spread is negative the doubling time is assumed to be infinite), C.) The adjusted R-squared estimates indicating the goodness of fit of the exponential regression model (with values closer to 1 indicating a better fit). Estimates are shown until the 2020-03-21. Light grey ribbon = 90% credible interval; dark grey ribbon = the 50% credible interval. Confidence in the estimated values is indicated by shading with reduced shading corresponding to reduced confidence.

Regional Breakdown

Data availability

Limitations

Summary of latest reproduction number and case count estimates


Figure 4: Cases with date of infection on the 2020-03-21 and the time-varying estimate of the effective reproduction number (bar = 90% credible interval). Regions are ordered by the number of expected daily cases and shaded based on the expected change in daily cases. The dotted line indicates the target value of 1 for the effective reproduction no. required for control and a single case required for elimination.

Reproduction numbers over time in the six regions with the most cases currently


Figure 5: Time-varying estimate of the effective reproduction number (light grey ribbon = 90% credible interval; dark grey ribbon = 50% credible interval) in the regions expected to have the highest number of incident cases. Estimates are shown up to the 2020-03-21. Confidence in the estimated values is indicated by shading with reduced shading corresponding to reduced confidence. The dotted line indicates the target value of 1 for the effective reproduction no. required for control.

Cases with date of onset on the day of report generation in the six regions with the most cases currently


Figure 6: Cases by date of report (bars) and estimated cases by date of infection (light grey ribbon = 90% credible interval; dark grey ribbon = 50% credible interval) in the regions expected to have the highest number of incident cases. Estimates are shown up to the 2020-03-21.Confidence in the estimated values is indicated by shading with reduced shading corresponding to reduced confidence.

Reproduction numbers over time in all regions


Figure 7: Time-varying estimate of the effective reproduction number (light grey ribbon = 90% credible interval; dark grey ribbon = 50% credible interval) in all regions. Estimates are shown up to the 2020-03-21. Confidence in the estimated values is indicated by shading with reduced shading corresponding to reduced confidence. The dotted line indicates the target value of 1 for the effective reproduction no. required for control.

Cases with date of onset on the day of report generation in all regions

Figure 8: Cases by date of report (bars) and estimated cases by date of infection (light grey ribbon = 90% credible interval; dark grey ribbon = 50% credible interval) in all regions. Estimates are shown up to the 2020-03-21. Confidence in the estimated values is indicated by shading with reduced shading corresponding to reduced confidence.

Latest estimates (as of the 2020-03-21)

State New infections Expected change in daily cases Effective reproduction no. Doubling time (days)
Alabama 1242 (364 – 2028) Increasing 2 (0.9 – 3) 5 (2.5 – 74)
Alaska 173 (39 – 283) Likely increasing 1.9 (0.9 – 2.9) 5.3 (2.7 – 310)
Arizona 977 (567 – 1332) Increasing 1.7 (1.1 – 2.2) 6.1 (3.7 – 15)
Arkansas 656 (232 – 1069) Likely increasing 1.7 (0.9 – 2.4) 6.8 (3.4 – Cases decreasing)
California 6715 (4271 – 8978) Increasing 1.6 (1.1 – 2) 7.3 (4.4 – 20)
Colorado 2995 (1246 – 4482) Increasing 1.7 (1 – 2.4) 5.9 (3.1 – 49)
Connecticut 2686 (896 – 4267) Increasing 1.9 (1 – 3) 4.8 (2.6 – 29)
Delaware 343 (101 – 580) Likely increasing 1.8 (0.9 – 2.8) 5.7 (2.8 – Cases decreasing)
District of Columbia 515 (195 – 814) Likely increasing 1.7 (0.9 – 2.4) 6.4 (3.2 – 220)
Florida 5821 (2506 – 8914) Increasing 1.8 (1 – 2.6) 5.4 (3 – 27)
Georgia 3358 (1474 – 4977) Increasing 1.7 (1 – 2.4) 6.1 (3.3 – 45)
Guam 99 (28 – 168) Likely increasing 1.8 (0.8 – 2.6) 6.4 (2.8 – Cases decreasing)
Hawaii 237 (89 – 388) Increasing 1.7 (0.9 – 2.4) 6.5 (3.3 – 230)
Idaho 492 (93 – 795) Increasing 2.1 (1 – 3.1) 4.5 (2.3 – 40)
Illinois 4568 (2972 – 6260) Increasing 1.6 (1.1 – 2.1) 6.5 (4 – 16)
Indiana 1964 (804 – 3098) Increasing 2 (1 – 2.9) 4.6 (2.5 – 27)
Iowa 447 (162 – 705) Increasing 1.8 (0.9 – 2.6) 5.6 (2.9 – 67)
Kansas 426 (151 – 667) Increasing 1.9 (1 – 2.8) 5.2 (2.8 – 49)
Kentucky 564 (226 – 868) Increasing 1.8 (1 – 2.6) 5.6 (3 – 46)
Louisiana 4879 (1653 – 7726) Likely increasing 1.8 (0.9 – 2.5) 5.8 (3 – 84)
Maine 350 (93 – 576) Likely increasing 1.7 (0.8 – 2.5) 6.5 (3 – Cases decreasing)
Maryland 1544 (548 – 2386) Increasing 1.9 (0.9 – 2.7) 5.1 (2.7 – 38)
Massachusetts 5146 (3189 – 7315) Increasing 1.8 (1.2 – 2.4) 5.4 (3.3 – 13)
Michigan 7500 (2335 – 12473) Increasing 1.9 (0.9 – 2.9) 5 (2.6 – 45)
Minnesota 688 (288 – 1109) Likely increasing 1.7 (0.9 – 2.3) 6.8 (3.5 – Cases decreasing)
Mississippi 1094 (365 – 1751) Likely increasing 1.8 (0.9 – 2.7) 5.5 (2.9 – 68)
Missouri 1233 (358 – 1909) Increasing 1.9 (1 – 3) 4.8 (2.6 – 51)
Montana 247 (50 – 398) Increasing 2 (0.8 – 2.9) 5 (2.5 – Cases decreasing)
Nebraska 169 (73 – 246) Increasing 1.5 (1 – 1.9) 8.7 (4.3 – Cases decreasing)
Nevada 1152 (404 – 1741) Increasing 1.8 (1 – 2.6) 5.5 (3 – 37)
New Hampshire 318 (139 – 481) Increasing 1.7 (1 – 2.3) 6.6 (3.5 – 56)
New Jersey 17113 (6620 – 26239) Increasing 1.9 (1 – 2.8) 4.8 (2.7 – 20)
New Mexico 353 (88 – 596) Likely increasing 1.8 (0.9 – 2.7) 5.6 (2.8 – Cases decreasing)
New York 73237 (32794 – 114100) Likely increasing 1.7 (0.9 – 2.4) 6.4 (3.3 – 62)
North Carolina 1407 (535 – 2123) Increasing 1.8 (1 – 2.5) 5.7 (3.1 – 54)
North Dakota 144 (41 – 248) Likely increasing 1.8 (0.8 – 2.7) 5.7 (2.8 – Cases decreasing)
Ohio 2227 (929 – 3681) Increasing 1.9 (1 – 2.8) 5.2 (2.8 – 45)
Oklahoma 560 (230 – 879) Increasing 1.9 (1 – 2.9) 4.9 (2.6 – 29)
Oregon 659 (307 – 994) Increasing 1.7 (1 – 2.3) 6.4 (3.5 – 40)
Pennsylvania 4342 (1749 – 6904) Increasing 1.9 (0.9 – 2.8) 4.8 (2.6 – 31)
Puerto Rico 202 (44 – 337) Increasing 2.1 (0.8 – 3.2) 4.6 (2.4 – 190)
Rhode Island 385 (171 – 590) Increasing 1.8 (1 – 2.5) 5.9 (3.2 – 38)
South Carolina 1012 (346 – 1542) Likely increasing 1.7 (0.9 – 2.5) 6.2 (3.2 – 150)
South Dakota 125 (31 – 200) Increasing 1.9 (1 – 2.8) 5.3 (2.7 – 130)
Tennessee 1995 (781 – 2991) Increasing 1.7 (1 – 2.5) 6 (3.2 – 41)
Texas 2886 (1755 – 4138) Increasing 1.7 (1.1 – 2.2) 6.2 (3.7 – 20)
Utah 816 (358 – 1206) Increasing 1.7 (1 – 2.3) 6.7 (3.5 – 57)
Vermont 318 (103 – 517) Increasing 1.8 (0.9 – 2.7) 5.9 (3 – 550)
Virginia 1170 (454 – 1868) Increasing 1.8 (0.9 – 2.5) 5.6 (3 – 48)
Washington 5023 (3253 – 6804) Increasing 1.5 (1.1 – 1.8) 9 (5.1 – 41)
West Virginia 219 (40 – 363) Likely increasing 2.2 (0.8 – 3.6) 4.3 (2.1 – Cases decreasing)
Wisconsin 1251 (746 – 1744) Increasing 1.5 (1 – 2) 7.5 (4.3 – 29)
Wyoming 137 (37 – 214) Likely increasing 1.8 (0.8 – 2.6) 5.8 (2.8 – Cases decreasing)


Table 2: Latest estimates (as of the 2020-03-21) of the number of cases by date of infection, the effective reproduction number, and the doubling time in each region. The mean and 90% credible interval is shown.

“2019 Novel Coronavirus Covid-19 (2019-nCoV) Data Repository.” 2020. Johns Hopkins CSSE. https://github.com/CSSEGISandData/COVID-19.

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Xu, Bo, Bernardo Gutierrez, Sarah Hill, Samuel Scarpino, Alyssa Loskill, Jessie Wu, Kara Sewalk, et al. n.d. “Epidemiological Data from the nCoV-2019 Outbreak: Early Descriptions from Publicly Available Data.” http://virological.org/t/epidemiological-data-from-the-ncov-2019-outbreak-early-descriptions-from-publicly-available-data/337.